Cmnt: [PATCH v1 1/1] [SRU][J:linux-bluefield][PATCH v1 1/1] UBUNTU: SAUCE: mlxbf-tmfifo: fix potential race

[Andrei Gherzan]

On 23/04/12 03:35PM, Liming Sun wrote:
> BugLink: https://bugs.launchpad.net/ubuntu/+source/linux-bluefield/+bug/2016039

This should be:

BugLink: https://bugs.launchpad.net/bugs/2016039

> 
> The fix adds memory barrier for the 'is_ready' flag and the 'vq'
> pointer in mlxbf_tmfifo_virtio_find_vqs() to avoid potential race
> due to out-of-order memory write.
> 
> Signed-off-by: Liming Sun <limings at nvidia.com>
> ---
>  drivers/platform/mellanox/mlxbf-tmfifo.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/platform/mellanox/mlxbf-tmfifo.c b/drivers/platform/mellanox/mlxbf-tmfifo.c
> index 97956c9c9d4c..19d539fc99ae 100644
> --- a/drivers/platform/mellanox/mlxbf-tmfifo.c
> +++ b/drivers/platform/mellanox/mlxbf-tmfifo.c
> @@ -922,7 +922,7 @@ static void mlxbf_tmfifo_rxtx(struct mlxbf_tmfifo_vring *vring, bool is_rx)
>  	fifo = vring->fifo;
>  
>  	/* Return if vdev is not ready. */
> -	if (!fifo->vdev[devid])
> +	if (!fifo || !fifo->vdev[devid])
>  		return;

This change is not mentioned in the git log. Sounds like an additional
patch to me.

>  
>  	/* Return if another vring is running. */
> @@ -1119,9 +1119,13 @@ static int mlxbf_tmfifo_virtio_find_vqs(struct virtio_device *vdev,
>  			goto error;
>  		}
>  
> +		vq->priv = vring;
> +
> +		/* Make vq update visible before using it. */
> +		virtio_mb(false);
> +
>  		vqs[i] = vq;
>  		vring->vq = vq;
> -		vq->priv = vring;
>  	}
>  
>  	return 0;
> @@ -1426,6 +1430,9 @@ static int mlxbf_tmfifo_probe(struct platform_device *pdev)
>  
>  	mod_timer(&fifo->timer, jiffies + MLXBF_TMFIFO_TIMER_INTERVAL);
>  
> +	/* Make all updates visible before the 'is_ready' flag. */
> +	virtio_mb(false);
> +
>  	fifo->is_ready = 1;
>  	return 0;
>  
> -- 
> 2.30.1

-- 
Andrei Gherzan
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